Temperature Light in dashboard came on, fan not turning. ICarsoft MBII Code meaning ?

[Submariner1]

2009 CL 500 W216 5.5L @ 52000 miles
5 months ago The temp warning light came on After driving 1 mile. The Temp rose from 90 to 95C. Fan not turning.
Stopped car, restarted and all was well, fan turning, temp dropped to its normal 90C .

Yesterday this happened again after driving 2 miles. I was 6 miles from home so decided to drive on, as the temp was lowish, the temp rose from 90C to circa 92C, traffic cleared and it stayed at 92 C.
I stopped car, the fan not working, restarted car fan still not turning, then the temp dropped to 80C for a few secs, then back to 90C, then flickered back at 85C, then rose instantly to 95 and then slowly dropped again to normal 90C. Stopped car and the fan was working And temp was normal.

As this time the temp rose and fell and rose fast and then increased slowly … I suspected a faulty temp sensor? Probably influenced by wishful thinking, as I guess the fan unit is hundreds of £s.

Next day hooked up the MBII reader, and had one historic fault.
And the code lookup said it was: as per pics

Q1. What does this fault code mean ? Any ideas ?
I.e. is it my temp sensor or the fan controller or the engine controller??

Q2. Is it OK to drive, if the engine temp is under 95C, as the dial shows Red sector starts at 120C?
no coolant loss. Manual says do not drive in red sector.

Q3. I have a crap battery, not changed as it starts the car, but if not driven for 3 days drops to 12.0V to 12.1V! Once started it goes to 14.5V instantly.
I have heard rumours if your battery is showing under 12.4V this can cause loads of Weird issues with control units. Is this true?
only asking as once the fan starts, it works fine for months.

Q4 As the temp sensor is only £24, plus an hours labour, is it worth changing that? , so I have peace of mind, if this fault is intermittent, at least I know the temp of the engine is accurate when ignoring the warning light. i.e. I would not drive it over 95C.
- I would hate to replace the whole fan unit at circa £800, on an intermittent fault. I would prefer to drive until it really fails , so I know the £800 had to be spent.

Q5. Will STAR show more accurate details to identify the actual faulty part? especially an historic fault. Asking as this car is old.


NB Not replaced Battery as this was a replaced one that failed. Loath to buy another crap one.

 

[Richard Moakes]

That code is indicative of the cooling fan controller going faulty. I doubt the temperature sensor will resolve the issue.

The ECM is calling for fan and it isn’t responding correctly.

Got to be a good shout to get a 2nd hand unit from W221 on eBay? Rather than spend £800

 

[Submariner1]

That code is indicative of the cooling fan controller going faulty. I doubt the temperature sensor will resolve the issue.

The ECM is calling for fan and it isn’t responding correctly.

Got to be a good shout to get a 2nd hand unit from W221 on eBay? Rather than spend £800

Thanks,
Do you think this low voltage issue could cause the fan controller to malfunction.
i.e. Is it worth recharging the battery first ( to get it from 12.1 volts to 12.5V ) to rule that out first?

 

[Submariner1]

Also is the Fan Controller an integral part of the whole fan unit.
on my EPC I couldn’t see a separate fan controller.

 

[Richard Moakes]

Thanks,
Do you think this low voltage issue could cause the fan controller to malfunction.
i.e. Is it worth recharging the battery first ( to get it from 12.1 volts to 12.5V ) to rule that out first?

Always worth having a fully charged battery, but did you have any low voltage codes? I would try that first, better than firing the parts cannon

 

[Richard Moakes]

I would also be looking at the cooling fan relay and fuse, checking for operation and any corrosion on the contacts, also check for corrosion on the fan power connector as well.

 

[Uncle Benz]

The fan module is built into the fan. They are common for trouble. It’s hard not having it in front of you, but I’m 90% it’s the fan.

 

[Submariner1]

The fan module is built into the fan. They are common for trouble. It’s hard not having it in front of you, but I’m 90% it’s the fan.

The fan module is built into the fan. They are common for trouble. It’s hard not having it in front of you, but I’m 90% it’s the fan.

Thanks

 

[Submariner1]

I would also be looking at the cooling fan relay and fuse, checking for operation and any corrosion on the contacts, also check for corrosion on the fan power connector as well.

Thanks where is that relay or is it built into thr fan module on the fan?

 

[Richard Moakes]

As per Uncle Benz, just checked, no relay, all fed from the big pre-fuse block near the battery, so money is on the module integrated into the fan which takes a pulse width modulated signal from the engine ECM to control fan speed.